Non-fluid conducting pressure module having non-contaminating body and isolation member

ABSTRACT

A non-contaminating pressure transducer module having an isolation member is disclosed. The isolation member isolates a pressure sensor within the transducer module from exposure to fluids flowing through a conduit in the module. The transducer module may be positioned in-line within a fluid flow circuit carrying corrosive materials, wherein the pressure transducer module produces a control signal proportional to either a gauge pressure or an absolute pressure of the fluid flow circuit. The pressure transducer module of the present invention also avoids the introduction of particulate, unwanted ions, or vapors into the flow circuit.

This is a Continuation application of application Ser. No. 08/538,478,filed on Oct. 3, 1995, now U.S. Pat. No. 5,693,887.

BACKGROUND OF THE INVENTION

I. Field of the Invention

This invention relates generally to pressure transducers. Moreparticularly, this invention relates to a pressure transducer moduleswhich may be connected in-line in a chemically corrosive fluid flowcircuit, wherein the pressure sensor used therein is isolated from thefluid flow circuit with a non-contaminating transducer body.

II. Discussion of the Related Art

During the production of semiconductors, the sensitivity tocontamination of materials used to produce them is a significant problemfaced by semiconductor manufacturers. Various processing systems havebeen designed to reduce the amount of foreign particles and vaporsgenerated during the processing of these sensitive materials. It iscritical that the semiconductor wafers be isolated from damagingparticulate and chemicals.

In an attempt to eliminate all sources of damaging contaminants, theequipment used to process the semiconductor wafers has necessarily beendesigned with this goal in mind. First, the various components of theprocessing equipment are commonly designed to reduce the amount ofparticulate generated and to isolate the processing chemicals fromcontaminating influences. The processing equipment commonly hasmonitoring and sensing devices connected in a closed loop feedback whichare used in monitoring and controlling the equipment. These monitoringand sensing devices must also be designed to eliminate any contaminationwhich might be introduced.

During the processing of semiconductor wafers, highly corrosivehazardous chemicals are commonly used. When these chemicals are used,extremely severe conditions within or near the processing environmentmay be encountered. Such corrosive atmospheric environments areextremely hard on the monitoring and sensing equipment. Further, themonitoring and sensing equipment may transmit wafer damagingparticulate, ions, or vapors as a result of exposure to the corrosiveatmospheric environment. Metals, which are conventionally used in suchmonitoring devices, cannot reliably stand up to the corrosiveenvironment for long periods to time. Hence, the monitoring and sensingdevices must incorporate substitute materials.

The highly corrosive environment may be created when hazardous chemicalsare delivered to the processing equipment. Liquid transporting systemscarry these chemicals from supply tanks through pumping and regulatingstations and through the processing equipment itself. The liquidchemical transport systems, which includes pipes, tubing, valves, andfittings and related devices, are frequently made of plastics resistantto the deteriorating effects of the toxic chemicals. Of course, anythingmechanical is subject to potential leakage and such leakage can createextremely hazardous conditions both to the processing of semiconductorwafers or other products and also to personnel who may have to tend andmaintain the processing equipment. Hence, the chemical transport systemmust be designed such that leakage is avoided. The monitoring andsensing devices may incorporate sensors which also must be designed toavoid the introduction of particulate, unwanted ions, or vapors into theprocessing steps.

An in-line mechanical fluid pressure responsive gauge separated from thefluid flow by a protective membrane is known in the art. The gauge iscontained within a housing having a cavity filled with a sensor fluid.The cavity is formed adjacent the fluid flow and separated by theprotective membrane. The sensor fluid contained within the cavity istypically a silicone oil. A change in pressure within the fluid flowaffects the oil pressure within the cavity. The oil pressure is detectedby the mechanical pressure responsive gauge.

The fluid within the cavity typically has large thermo-expansions whichcause large deflection changes in the protective membrane. The largedeflection changes in the protective membrane increases the likelihoodthat the fluid within the cavity will leak into the fluid flow,contaminating the flow circuit. Also, the accuracy of the pressure gaugeis negatively affected by the large thermo- expansions of the sensorfluid. Hence, a need exists for an in-line pressure gauge that does notleak contaminating fluids into the fluid flow circuit. Also, a needexists for a pressure gauge, wherein the accuracy is not affected bythermo- changes within the fluid flow circuit.

Collins et al., in U.S. Pat. No. 5,316,035 (the '035 patent) describesthe use of a capacitance proximity monitoring device in corrosiveatmosphere environments. In one embodiment of the '035 patent, thecapacitance proximity device is described as being incorporated into afunctional apparatus, such as a valve or coupling for tubing. Thecapacitance proximity device serves as a functional portion of theapparatus and creates a sensing field within a predetermined area. It isthen used to determine the change of electrical characteristics withinthe predetermined area as various fluids flow past the predeterminedarea. The current related to the sensing field changes when the liquidtarget media is present, versus air or gas in the tubing when the liquidtarget media is absent, thereby producing an indication of the presenceor absence of the target media. The complex valving often includes afluid which may leak into and contaminate the processing fluid flow.

The '035 patent does not disclose or even consider a device capable ofdetermining various pressures within the chemical transport system ofthe processing equipment. Monitoring the pressure within the chemicaltransport system is useful for several reasons. First, a change inpressure within the system may be indicate leakage within the system.Second, the pressure within the transport system is regulated to avoidexceeding predetermined safety limits. Third, the pressure within afluid flow circuit may be controlled to actuate various processing toolsconnected to the processing equipment.

Therefore, a need exists for a non-contaminating pressure transducerwhich may be positioned in-line within a fluid flow circuit carryingcorrosive materials, wherein the pressure transducer determines either agauge pressure or absolute pressure of the fluid flow circuit. A needalso exists for a pressure transducer that avoids the introduction ofparticulate, unwanted ions, or vapors into the flow circuit. The presentinvention overcomes these and other disadvantages of the related art.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a pressure transducermodule that may be coupled in-line to a flow circuit of corrosive fluid,wherein either the gauge pressure or absolute pressure within the flowcircuit may be determined. The pressure transducer module includes apressure sensor within an non-contaminating body. In the preferredembodiment, the components of the pressure transducer module includes ahousing, a cap, an electrical connector, pressure fittings, an isolationmembrane, a pressure sensor, electronic circuitry, a spacer ring and ahold down ring.

The cap of the housing is removably attached to the housing by matingthreads formed on an internal surface of the cap and on the externalsurface of the housing. An electrical connector is mounted into thecover, allowing electrical leads within the housing to mate withexternal conductors when the cover is attached.

The housing has a bore extending therethrough, which forms a passage orconduit through which fluids flow, when the transducer is connectedin-line within a fluid flow circuit. Aligned and sealably connected toeach open end of the bore are pressure fittings. The pressure fittingsare constructed from a chemically inert material and are readilyavailable and known to those skilled in the art. The housing also has acavity extending from an external surface thereof in communication withthe bore. A lip is preferably formed in the housing at the intersectionof the cavity and bore. The lip has an inner dimension that is less thanthe inner dimension of the housing. The isolation membrane, pressuresensor, electronic circuit, spacer ring and hold down ring are allcontained within the cavity of the housing.

The isolation membrane is sealed against the lip of the housing withinthe cavity. In this manner, the cavity of the housing is isolated fromthe fluid flow. The isolation membrane is preferably constructed of ananti-corrosive, chemically inert material with Polytetrafluoroethylenebeing preferred. The pressure sensor is bonded, pressed, heat welded orotherwise attached to the isolation membrane. The pressure sensor may beof a capacitance or piezoelectric type. A hybrid or fully integratedelectronic circuit disposed in the housing is operatively coupled to thepressure sensor and to the aforementioned connector.

The electronic circuit develops a signal which is a measure of thepressure within the flow circuit from information sensed by the pressuresensor. This electronic circuit may also be used in combination withtemperature sensitive components to adjust the pressure measurementbased upon temperature changes within the flow circuit. As mentioned,the electronic sensor is coupled by electrical leads to the electricalconnector and power may be transmitted to the electronic circuit throughthe electrical leads mating at the connector with an external powersupply. Further, an analog output such as a standard 4-20 milliampssignal proportional to the calculated pressure may be transmittedthrough additional electrical leads.

The isolation membrane and pressure sensor are contained within thecavity by a combination of the spacer ring and hold down ring. The holddown ring has threading formed on its surface that mates with threadingformed on the internal surface of the valve body defining the cavity.

Without limitation, the housing, isolation membrane, spacer ring, andhold down ring are constructed of the same polymer to avoid leakage whenthe transducer is subject to thermal expansion. In the preferredembodiment tetrafluoroethylene fluorocarbon polymers are used. Thesepolymers reduce the amount of abraded particulate, are chemically inert,and provide a non-contaminating pressure transducer module.

OBJECTS

It is accordingly a principal object of the present invention to providea non-contaminating pressure transducer adapted to be connected in-linein a fluid flow circuit.

Another object of the present invention is to provide a pressuretransducer module wherein its pressure sensor component is isolated fromthe fluid flow circuit by a non-contaminating barrier.

Yet another object of the present invention is to provide a pressuretransducer module having an isolation member that is in direct contactwith a pressure sensor, the isolation member acting to isolate thesensor and associated electronic circuitry from potentially corrosiveprocessing chemicals and precluding introduction of contaminatingsubstances into the processing fluids being transported.

Still another object of the present invention is to provide a pressuretransducer wherein a gauge pressure or absolute pressure of the flowcircuit is measured non-intrusively.

These and other objects, as well as these and other features andadvantages of the present invention will become readily apparent tothose skilled in the art from a review of the following detaileddescription of the preferred embodiment in conjunction with theaccompanying drawings and claims and in which like numerals in theseveral views refer to corresponding parts.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the pressure transducer;

FIG. 2 is a side elevational view of the pressure transducer of the typeshown in FIG. 1;

FIG. 3 is a partial, sectioned side elevational view of the pressuretransducer module of the type shown in FIG. 1 having the cap removed;

FIG. 4 is an enlarged partial, sectioned view of the pressure transducermodule shown in FIG. 3;

FIG. 5 is a perspective view of the flexible membrane used in theassembly of FIGS. 1 through 3;

FIG. 6 is a side view of an alumina ceramic capacitive pressure sensor;

FIG. 7 is an enlarged partial, sectioned side elevational view of analternate preferred pressure transducer module in accordance with afurther embodiment of the invention;

FIG. 8 is an enlarged, partial, sectioned side elevational view ofanother alternate preferred pressure transducer module;

FIG. 9 is an enlarged, partial sectioned side elevational view of stillanother preferred pressure transducer module;

FIG. 10 is yet another enlarged, partial sectioned, side elevationalview of a still further alternate preferred pressure transducer module;

FIG. 11 is an enlarged, partial, sectioned side elevational view of yetanother pressure transducer module constructed in accordance with thepresent invention;

FIG. 12 is an enlarged, partial sectioned side elevational view of yet afurther alternate preferred pressure transducer module.

FIG. 13 is an enlarged, partial sectioned side elevational view of yet afurther alternate preferred pressure transducer module;

FIG. 14 is an enlarged, partial sectioned side elevational view of yet afurther alternate preferred pressure transducer module; and

FIG. 15 is an enlarged, partial sectioned side elevational view of yet afurther alternate preferred pressure transducer module.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring first to FIGS. 1 and 2, the pressure transducer module isgenerally identified by numeral 10. The pressure transducer is shown ashaving a base 12 which is used in mounting the pressure transducermodule 10 to processing equipment (not shown). The module generallyincludes a housing or body 14, pressure fittings 16 and 18 and a coveror cap 20. An electrical connector 22 of known construction may beremovably attached to the cover 20. The pressure fittings 16 and 18serve as a inlet and a outlet to the transducer body 14 and are of knownconstruction.

Those skilled in the art will recognize that the pressure transducerhousing may take on various shapes, however a generally cylindricalshape as shown is preferred. A cylindrical pressure transducer body iseasily manufactured and fluids flow more readily through a cylindricalbore or cavity within the transducer. The housing 14 and cover 20 arepreferably manufactured from a chemically-inert, non-contaminatingpolymer such as a polytetrafluoroethylene.

The cover may have threading formed on an internal surface that mateswith threading as at 24 in FIG. 3 formed on an external surface of thehousing. The cover may thus be screwed to the housing and may furtherhave a suitable o-ring seal (not shown) positioned therebetween to allowthe cover to be hermetically sealed to the housing. A vent 26, shown inFIG. 2, may be formed through the housing wall, thereby venting aninterior of the housing. The vent 26 allows a pressure sensor containedwithin the housing to determine a gauge pressure. Without such a ventabsolute pressure within the fluid flow circuit is measured. Theparticular features of the various components of pressure transducerwill now be discussed.

Referring to FIGS. 3 and 4, the internal construction of the pressuretransducer is shown. A bore 28 extends through the housing forming aconduit, whereby when the pressure transducer module 10 is connectedin-line, with a fluid flow circuit, via pressure fittings 16 and 18, thebore 28 serves as a passage within the fluid flow circuit. One end ofthe bore opening forms the inlet and the other end of the bore forms anoutlet to the fluid flow circuit. The orientation of the pressuretransducer module within the fluid flow circuit may be reversed withoutaffecting the effectiveness of the pressure transducer.

A cavity 30 extends all the way from an outer surface of the housing 20to the bore 28. Near the region within the housing where the cavity 30and the bore 28 intersect, an annular lip 32 is formed. The lip 32further defines an opening to the cavity from the bore. As furtherdiscussed below, the lip may have various shapes.

A thin flexible polymer disk membrane 34 is positioned on the lip 32 ofthe cavity. In the preferred embodiment both the housing 14 and theflexible membrane 34 are manufactured from tetrafluoroethylenefluorocarbon polymers. One such tetrafluoroethylene fluorocarbon polymeris sold under the TEFLON® trademark by E. I. duPont Nemours. In thepreferred embodiment, the disk membrane is preferably molded rather thansprayed or manufactured by some other process that may leave pinholepaths therein. When the pressure transducer module is fully assembled,the annular surface contact between the flexible membrane and thehousing lip 32 is such that a hermetic seal is formed therebetween.

Referring next to FIG. 5, the thin, flexible, Teflon membrane 34 isshown in greater detail. Without limitation, the membrane is preferablyconstructed to have a thickness in a range between 0.001 and 0.040inches. The upper surface 36 is abraded so as to create a pattern ofgrooves or channels. Now, when the upper surface 36 of the membrane ispressed against the base 38 of the pressure sensor 40, any air pocketsthat might otherwise have formed between the sensor base 38 and themembrane are relieved, allowing more intimate contact between themembrane and the pressure sensor 40. The flange 52 of the spacer 50 andthe o-ring 54 are dimensioned to allow a slight gap between the sensor40, o-ring 54, and spacer 50. The inner surface of the spacer 50 mayalso have a pattern of grooves or channels formed thereon, therebycreating a passage for the relieved air to escape into a central regionof the cavity.

Referring again to FIGS. 3 and 4, the pressure sensor 40 is positionedon top of the flexible membrane 34. The pressure sensor may be of acapacitance type or piezoelectric type known to those skilled in theart. The base 38 of the pressure sensor is in direct contact with themembrane and may be either in pressure contact with or bonded to themembrane by an adhesive, thermal welding or by other known means.

In one embodiment generally shown in FIG. 6, an alumina ceramic pressuresensor is comprised of a thin, generally compliant ceramic sheet 42having an insulating spacer ring 44 sandwiched between a thicker,non-compliant ceramic sheet 46. The first thin ceramic sheet ordiaphragm is approximately 0.005 to 0.050 inches in thickness with atypical thickness of 0.020 inches. The thicker ceramic sheet has athickness range between 0.100 to 0.200 inches. The spacer may beconstructed of a suitable polymer. The apposed faces of ceramic disks 42and 46 are metalized by metals such as gold, nickel or chrome to createplates of a capacitor. A similar capacitive pressure transducer isdescribed by Bell et al. in U.S. Pat. No. 4,177,496 (the '496 patent).Other capacitive pressure transducers similar to that described in the'496 patent are available and known in the art.

Referring again to FIG. 4, an electronic circuit module 48 is positionedabove the ceramic pressure sensor 40 and is electrically coupled to theconductive surfaces of the ceramic pressure sensor. The electroniccircuit module 48 is also connected by suitable leads, not shown tointerval contacts of the connector 22 (FIG. 1). In the preferredembodiment the electrical connector 22 is made of a chemically inertmaterial and preferably may be of a type available from Pneumatico, partnumber po3rsd-00004-24.

The electronic circuit module 48 develops a control signal proportionalto the pressure within the flow circuit using analog informationreceived from the pressure sensor 40 related to changes in itscapacitance due to deformation of member 42 by the fluid pressure actingon it. The electronic circuit may also adjust the pressure as thetemperature within the flow circuit changes by including a thermistor orlike component therein.

In FIGS. 3 and 4, a cup shaped spacer member 50 is disposed above thepressure sensor 40 so as to exert a force on the upper surface of thepressure sensor 40, holding the sensor flat against the membrane 34. Thespacer 50 further has a circumferential flange 52 (FIG. 4) whichtransfer a force against the membrane 34 and lip 32 of the cavity. Ano-ring 54 may be positioned between the flange 52 of the spacer and themembrane, wherein through its elastomeric properties, the force may betransferred from the spacer member 50 against the membrane to clamp itagainst the annular cavity lip 32. A threaded hold down ring 56 isrotated in mating relation with the inner threads of the cavity of thehousing or body 14, thereby engaging the spacer member 50 and forcing itagainst the pressure sensor 40 and membrane 34.

In order to reduce dead space, the distance “d” (FIG. 4) that theflexible membrane is displaced from the lumen of the bore 28 should bekept to a minimum. The decrease in dead space reduces the chance ofaccumulation of debris and contamination. The decrease in dead spacealso reduces or eliminates the chance of air bubbles being trapped inthe dead space and then suddenly released back into the flow circuit.The release of these air bubbles from the dead space has a negativeimpact on the semiconductor processing. The inner diameter of the lumen“D” should be equal to or exceed 2*(d). Ideally, the dimension, d, willbe far less than the dimension, D, in measurement.

FIG. 7 shows an alternative embodiment wherein the spacer member 50 hasrounded edges as at 58. The rounded edges help focus the force of thespacer 50 against the flexible membrane 34 and the lip 32 of the cavity.This arrangement also eliminates the need for the o-ring 54. However,o-ring 54 may be positioned between the membrane and the lip 32 (seeFIG. 13). The flange 52 of the spacer 50 and the o-ring 54 aredimensioned to allow a slight gap between the sensor 40, o-ring 54, andspacer 50. The inner surface of the spacer 50 may also have a pattern ofgrooves or channels formed thereon, thereby creating a passage for therelieved air to escape. Further, the spacer 50′ may have a boreextending through a center section, thereby extending the passage intothe cavity of the housing.

FIG. 8 illustrates another preferred embodiment wherein the lip 32′ ofthe cavity is stepped. The o-ring 54, when compressed by the spacermember 50, is made to conform to the shape of the step and pushes orforces the flexible membrane 34, causing it to bend and mold to theshape of the stepped lip 32 to provide a seal against ingress of fluid.In yet another embodiment, the o-ring 54 may be positioned between themembrane and the lip 32′ (see FIG. 15).

FIG. 9 illustrates another preferred embodiment having the end of thespacer member flange 52 rounded, wherein the flange is forced againstthe o-ring 54 which, in turn, forces the o-ring against the flexiblemembrane 34.

FIG. 10 illustrates yet another preferred embodiment wherein the o-ringseal 54′ is contained within an annular groove or recess 60 formedwithin the lip 32′. The flexible membrane 34 is forced against theo-ring 54′, sealing the edges of the lip 32′ thereby preventing thefluid of the flow circuit from leaking into the cavity of the housing.This shield arrangement is preferred in circumstances where the fluidflow pressure is less than the atmospheric pressure. In such acircumstance, the shield arrangement eliminates the possibility of theo-ring being drawn into the fluid flow circuit.

FIG. 11 illustrates yet another embodiment wherein an annular ridge 62is formed along the surface of the lip 32. When the membrane iscompressed against the lip, the membrane conforms to the shape of theridge. In this manner, an effective seal is formed between the membranesheet and the housing lip.

FIG. 12 shows yet another embodiment wherein the lip has a multiple stepwherein the o-ring 54 is positioned on the lower step below the membrane34. An additional annular sealing ring 64 having an external groove 66for receiving an o-ring 68 and an internal groove 70 for receiving ano-ring 72 provides an additional seal between the housing 14 and thepressure sensor 40. The additional annular sealing ring 64 is shown asbeing positioned between a top step 74, and the first spacer ring 76.The spacer member 50 is in direct contact with both the first spacerring 76 and the pressure sensor 40. In this manner, the interior of thehousing is sealed from the fluid circuit independently of the sealcreated between the membrane 34 and the pressure sensor 40. A drainchannel 78 extends through the housing 14 to an external surface. Thedrain channel 78 is positioned between the top step 74 and the lowerstep to which the seal 54 is in contact. If fluid from the flow circuitleaks past o-ring 54, the drain channel 78 allows this fluid to drainout of the housing without contaminating or affecting the sensor 40.

When the o-ring 54 is positioned on the fluid flow circuit side (seeFIGS. 10 and 12-15), the o-ring must be manufactured from a chemicallyinert material. A perfluoroelastomer, such as KALREZ available fromduPont Nemours, Inc., is suitable for this purpose. Other materials suchas CHEMRAZ, an elastomeric PTFE available from Greene, Tweed & Co., Inc.is equally suitable.

Having described the constructional features of the present inventionthe mode of use will now be discussed. The user couples the pressuretransducer module 10 into a fluid flow circuit through pressure fittings16 and 18. As fluid flows through the flow circuit, the pressuredistorts the thin ceramic plate 38 of the pressure sensor 40 as afunction thereof, and thus changes the capacitance of the ceramicpressure sensor. The change in capacitance is related to the pressurewithin the flow circuit. This change in capacitance is detected by theelectric circuit 48 which, in turn, produces an analog signalproportional to the pressure. The gauge pressure or absolute pressuremay equally be determined.

Those skilled in the art will recognize that the transducer output maybe calibrated so that minimum output values are associated with minimumpressure and maximum output pressures are associated with maximumpressure. For example, a transducer intended to measure 0 to 100 psig(pounds per square inch gauge) can be calibrated to read 4 mA(milliamps) at 0 psig and 20 mA at 100 psig.

By providing the inert Teflon membrane which is in intimate contact withthe ceramic diaphragm 38 of the pressure sensor, the working fluid doesnot contact the surfaces of the sensor which could lead tocontamination. The sealing arrangements disclosed insure that theworking fluid does not enter the cavity of the housing 14 and adverselyaffect the electronic circuity.

This invention has been described herein in considerable detail in orderto comply with the patent statutes and to provide those skilled in theart with the information needed to apply the novel principles and toconstruct and use such specialized components as are required. However,it is to be understood that the invention can be carried out byspecifically different devices, and that various modifications, both asto the equipment details and operating procedures, can be accomplishedwithout departing from the scope of the invention itself.

What is claimed is:
 1. A chemically inert pressure transducer moduleadapted to be connected in-line with a fluid flow circuit, comprising:(a) a chemically inert housing having a bore extending through at leasta portion of said housing, wherein an inlet end of said bore isconnected in-line to the fluid flow circuit, said housing further havinga cavity formed within said housing extending from an outer surface ofsaid housing toward the bore of said housing; (b) a removable chemicallyinert flexible isolation member separating said cavity and said bore,the isolation member having first and second opposed major surfaces,said first major surface being exposed to fluid flowing in the circuit,said second major surface adjacent and adjoining non-fluid conductingmeans for sensing a pressure within the flow circuit; (c) said non-fluidconducting means for sensing a pressure within the flow circuit beingisolated from fluid flowing in the circuit; (d) means for constrainingthe isolation member and the non-fluid conducting means for sensing in afixed position within the cavity of the housing; and (e) an electroniccircuit contained within the cavity of the housing and coupled to thenon-fluid conducting means for sensing a pressure within the flowcircuit, whereby the electronic circuit produces an electrical signalproportional to the pressure within the bore.
 2. The pressure transducermodule is recited in claim 1, wherein said isolation member ismanufactured from a fluorocarbon polymer.
 3. The pressure transducermodule as recited in claim 1, wherein said housing and said means forconstraining are manufactured from a chemically inert polymer.
 4. Thepressure transducer module as recited in claim 3, wherein saidchemically inert polymer comprises polytetrafluoroethylene.
 5. Thepressure transducer module as recited in claim 1, wherein the means forsensing comprises a capacitive sensor.
 6. The pressure transducer moduleas recited in claim 1, wherein the means for sensing comprises apiezoelectric sensor.
 7. The pressure transducer module as recited inclaim 1, wherein the electronic circuit includes a means for adjustingthe control electrical signal to compensate for fluctuations intemperature within the flow circuit.
 8. The pressure transducer moduleas recited in claim 1, wherein said isolation member includes aplurality of channels formed on an upper surface of said isolationmember, said channels extending from one edge of said member to anotherspaced apart edge of said member.
 9. The pressure transducer module asrecited in claim 1, wherein the housing further has a drain channelextending from the outer surface of the housing into the cavity betweenfirst and second sealing members.
 10. The pressure transducer module isrecited in claim 1, wherein said isolation member has a thicknessdimension ranging between 0.001 and 0.040 inches.
 11. The pressuretransducer module as recited in claim 10, wherein the housing furtherhas a drain channel extending from the outer surface of the housing intothe cavity between a sealing member which seals the pressure sensor tothe housing and the isolation member.
 12. A chemically inert pressuretransducer module adapted to be connected in-line within a chemicallycorrosive ultra high purity fluid flow circuit, comprising: (a) achemically inert housing having a bore extending through at least aportion of said housing, wherein an inlet end of said bore is connectedin-line to the fluid flow circuit, said housing further having a cavityformed therein and extending from an outer surface of said housingtoward the bore of said housing; (b) a non-fluid conducting pressuresensor positioned within said cavity adjacent said bore for sensing apressure within the fluid flow circuit; (c) a removable chemically inertisolation member separating said cavity and said bore, said isolationmember having first and second opposed major surfaces, said first majorsurface being exposed to fluid flowing in the bore, said second majorsurface being adjacent to and adjoining the pressure sensor to saidisolation member, thereby isolating the pressure sensor from fluidcommunication with the bore; and (d) means for producing an electricalsignal proportional to the pressure within the bore coupled to saidpressure sensor.
 13. The pressure transducer module as recited in claim12, wherein the pressure sensor comprises a capacitive sensor.
 14. Thepressure transducer module as recited in claim 12, wherein the pressuresensor comprises a piezoelectric sensor.
 15. The pressure transducermodule as recited in claim 12, wherein the means for producing anelectrical signal includes a means for adjusting the control electricalsignal to compensate for fluctuations in temperature within the flowcircuit.
 16. The pressure transducer module as recited in claim 12,wherein said isolation member includes a plurality of channels formed onan upper surface of said isolation member, said channels extending formone edge of said member to another spaced apart edge of said member. 17.The pressure transducer module as recited in claim 12, wherein thehousing further has a drain channel extending from the outer surface ofthe housing into the cavity between first and second sealing members.18. The pressure transducer module as recited in claim 12, wherein saidisolation member has a thickness dimension ranging between 0.001 and0.040 inches.
 19. A chemically inert pressure transducer module adaptedto be connected in-line within a chemically corrosive ultra high purityfluid flow circuit, comprising: (a) a chemically inert housing having abore extending through at least a portion of said housing, wherein aninlet end of said bore is connected in-line to the fluid flow circuit,said housing further having a cavity formed therein and extending froman outer surface of said housing toward the bore of said housing: (b) anon-fluid conducting pressure sensor positioned within said cavityadjacent said bore for sensing a pressure within the fluid flow circuit;(c) a chemically inert isolation member separating said cavity and saidbore, said isolation member having first and second opposed majorsurfaces, said first major surface being exposed to fluid flowing in thebore, said second major surface being adjacent to and adjoining thepressure sensor, thereby isolating the pressure sensor from fluidcommunication with the bore; (d) a first sealing member to sealablyengage said isolation member to said housing; and (e) a second sealingmember to sealably engage said pressure sensor to said housing.
 20. Thepressure transducer module as recited in claim 19, wherein the housingfurther has a drain channel extending from the outer surface of thehousing into the cavity between first and second sealing members. 21.The pressure transducer module as recited in claim 19, wherein saidisolation member has a thickness dimension ranging between 0.001 and0.040 inches.
 22. A chemically inert pressure transducer module adaptedto be connected in-line with a fluid flow circuit, comprising: (a) ahousing having a bore extending through at least a portion of saidhousing, wherein an inlet end of said bore is coupled in-line to a fluidflow circuit, said housing further having a cavity formed therein, adrain channel extending from an outer surface of the housing into thecavity; (b) a removable isolation member separating the bore and cavityof said housing; (c) a non-fluid conducting pressure sensor at leastpartially contained within the cavity of said housing and in contactwith said isolation member; and (d) means for producing a signalproportionate to a measured pressure within the bore.
 23. The pressuretransducer module as recited in claim 22, wherein said housing ischemically inert.
 24. The pressure transducer module as recited in claim22, wherein the means for producing a signal includes a means foradjusting the signal to compensate for fluctuations in temperaturewithin the flow circuit.
 25. The pressure transducer module as recitedin claim 22, wherein said isolation member includes a plurality ofchannels formed on an upper surface of said member, said channelsextending from one edge of said member to another spaced apart edge ofsaid member.
 26. The pressure transducer module as recited in claim 22,wherein the non-fluid conducting pressure sensor is of a capacitivetype.
 27. The pressure transducer module as recited in claim 22, whereinthe non-fluid conducting pressure sensor is of a piezoelectric type. 28.The pressure transducer module as recited in claim 22, wherein thehousing further has a drain channel extending from an outer surface ofthe housing into the cavity.
 29. The pressure transducer module asrecited in claim 22, wherein said isolation member has a thicknessdimension ranging between 0.001 and 0.040 inches.
 30. The pressuretransducer module as recited in claim 22, wherein the housing furtherhas a drain channel extending from an outer surface of the housing intothe cavity between a sealing member which seals the pressure sensor tothe housing and the isolation member.
 31. The pressure transducer moduleas recited in claim 22, wherein said isolation member is removable. 32.The pressure transducer module as recited in claim 31, 30, furtherincluding a sealing member positioned between said isolation member andsaid housing.
 33. A chemically inert pressure transducer module adaptedto be connected in-line within a chemically corrosive ultra high purityfluid flow circuit, said module comprising: (a) a housing having a boreextending through at least a portion of said housing wherein an inletend of said bore is adaptable for connection to the fluid flow circuit;(b) a non-fluid conducting pressure sensor positioned within saidhousing for sensing a pressure within the fluid flow circuit; (c) anisolation member isolating said pressure sensor within said housing fromsaid bore, said isolation member having first and second opposed majorsurfaces, said first major surface being exposed to fluid flowing in thebore, said second major surface supporting the pressure sensor; (d)means for producing an electrical signal proportional to the pressurewithin the bore coupled to said pressure sensor; and (e) a ventextending from an outer surface of said housing into a chamber of saidhousing, wherein a portion of said pressure sensor is isolated withinsaid chamber.
 34. The pressure transducer module as recited in claim 33,wherein the pressure sensor comprises a capacitive sensor.
 35. Thepressure transducer module as recited in claim 33, wherein the pressuresensor comprises a piezoelectric sensor.
 36. The pressure transducermodule as cited in claim 33, wherein the means for producing anelectrical signal includes a means for adjusting the electrical signalto compensate for fluctuations in temperature within the flow circuit.37. The pressure transducer module as recited in claim 33, wherein saidisolation member includes a plurality of channels formed on an uppersurface of said isolation member, said channels extending from one edgeof said member to another spaced apart edge of said member.
 38. Thepressure transducer module as recited in claim 33, wherein said ventextends into said chamber of said housing between first and secondsealing members.
 39. The pressure transducer module as recited in claim33, wherein said isolation member has a thickness dimension rangingbetween 0.001 and 0.040 inches.
 40. A chemically inert pressuretransducer module adapted to be connected in-line within a chemicallycorrosive ultra high purity fluid flow circuit, said pressure transducermodule comprising: (a) a housing having a bore extending through atleast a portion of said housing, wherein an inlet end of said bore isadaptable for connection to a fluid flow circuit; (b) a non-fluidconducting pressure sensor positioned within said housing for sensing apressure within the fluid flow circuit; (c) an isolation memberisolating said pressure sensor within said housing, said isolationmember having first and second opposed major surfaces, said first majorsurface being exposed to fluid flowing in the bore, said second majorsurface supporting the pressure sensor, thereby isolating the pressuresensor from fluid communication with the bore; (d) a vent extending froman outer surface of said housing into a first chamber of said housing,wherein a portion of said pressure sensor is isolated within said firstchamber from a remainder of an internal portion of said housing; and (e)an electrical circuit contained within a second chamber of said housingand coupled to said pressure sensor, said electrical circuit produces anelectrical signal proportional to the pressure within the bore.
 41. Thepressure transducer module as recited in claim 40, wherein the pressuresensor comprises a capacitive sensor.
 42. The pressure transducer moduleas recited in claim 40, wherein the pressure sensor comprises apiezoelectric sensor.
 43. The pressure transducer module as recited inclaim 40, wherein the electrical circuit includes a means for adjustingthe electrical signal to compensate for fluctuations in temperaturewithin the flow circuit.
 44. The pressure transducer module as recitedin claim 40, wherein said isolation member includes a plurality ofchannels formed on an upper surface of said isolation member, saidchannels extending from one edge of said member to another spaced apartedge of said member.
 45. The pressure transducer module as recited inclaim 40, wherein said vent extends into said chamber of said housingbetween first and second sealing members.
 46. The pressure transducermodule as recited in claim 40, wherein said isolation member has athickness dimension ranging between 0.001 and 0.040 inches.
 47. Thepressure transducer module as recited in claim 40, further including asecond vent extending from an external surface of said housing into saidsecond chamber.